This invention relates to cross-linked hydrophilic polymeric films, the process of making such films, and their use in applications where strength of the polymer article and high permeability to water are required simultaneously. In particular, these films are suitable for use as a carrier for biologically active agents, such as pharmaceuticals, both human and veterinary, insecticides, and fertilizers; as hydrophilic membranes for separation processes; as bandages for wound treatment; as body implants or as coatings for such implants; and as coatings on glass, metal, wood or ceramics.
Such films, particularly when used as biological carriers, should not only be able to entrap the biological agent, but should also be biocompatible; that is, both mild and non-cytotoxic to living organisms. Additionally, they should be chemically and mechanically stable.
Cross-linked polymeric films have been made. For example, U.S. Pat. Nos. 2,976,576 and 3,220,960 disclose cross-linked hydrophilic polymers which are produced by polymerizing a hydrophilic monomer in the presence of a cross-linking agent; U.S. Pat. No. 3,520,94 discloses hydrophilic cross-linked polymers which are produced by admixing a water-soluble polymerizable hydroxyalkyl monoester of a mono-olefinic monocarboxylic acid and a polymerizable diester of a mono-olefinic monocarboxylic acid in the presence of a linear polyamide; and U.S. Pat. Nos. 4,192,827 and 4,277,582 disclose cross-linked polymers which are produced from a polymer of mono-olefinic monomers or copolymer of mono-olefinic monomers which is cross-linked with a terminal diolefinic hydrophobic macromer. However, the use of monomers is disadvantageous in the pharmaceutical industry due to the potential cytotoxicity of unreacted monomers.
Other cross-linked polymeric films have been made from polymers, thereby overcoming the problem of unreacted monomers. For example. WO 93/09176 discloses cross-linking of polysaccharides, polycations and lipids with polymerizable acrylate in the presence of a radical initiator by using certain sources of energy; U.S. Pat. No. 3,077,468 discloses the method of cross-linking water-soluble hydroxyalkyl polysaccharide ethers by reacting them with an insolubilizing agent selected from unsaturated dibasic aliphatic acids and their anhydrides and the water-soluble derivatives of said acids and their anhydrides; and U.S. Pat. No. 3,272,640 discloses cross-linking water-soluble polymers by reacting them with a hydrophobic film former.